<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    let a=prompt("请输入您的成绩");
    if(a>=90){
        alert("优秀");
    }else if(a>=80){
        alert("良好");
    }else if(a>=60){
        alert("及格");
    }else{
        alert("不及格");
    }
</script>
</body>
</html>